This invention relates to an imaging device employing so-called transfer type pressure-sensitized recording medium consisting of a microcapsule sheet (pressure-sensitized medium) and a developing sheet or a self-developing type pressure-sensitized recording medium, more particulary, to an imaging device having a function capable of controlling an operation of a pressurizing rollers for pressurizing medium so as to begin to accurately pressurize the recording medium from the start position of an area to be pressurized.
An imaging device employing a pressure-sensitized recording medium consisting of a microcapsule sheet and a developing sheet will be described below for an example of conventional devices.
The microcapsule sheet forms a roll with its leading end to be pulled out of it in operation. The developing sheet is in cut form.
Such an imaging device generates through exposure a latent image responsive to the actual image on the microcapsule sheet. A developing sheet is then laid on the side carrying the latent image of the microcapsule sheet and both are pressurized between a pair of pressure rollers opposed to each other. This pressure operation develops the latent image formed on the microcapsule sheet into a visible image transferred to the developing sheet.
The pair of pressure rollers are normally in their standby open position, while drawing themselves to a closed position when a sensor, for instance, detects the developing paper passing a certain position having been set before the pair of the pressure rollers. The pressure rollers resume their open position when they are rotated through a certain angle after closure thereof.
However, there are some cases in which adjusting the degree of exposure of the pressure-sensitized recording medium or enlarging or reducing the image size is effected by varying a travelling speed of the pressure-sensitized recording medium. As the travelling speed thus varies, there is some irregularity in feed quantity of the developing medium and the pressure-sensitized recording medium into the space between the pressure rollers when the opposing pressure rollers of the pressure developing unit are completely brought to their closing position.
This makes the pressure-developing operation on the developing sheet start at varying start positions, resulting in a difficulty in providing an exact reproduction of the image.
Also, when employing a pressure-sensitized recording medium consisting of microcapsule sheet and developing sheet, a problem has been encountered that, if a sheet of microcapsule sheet with no developing sheet laid on it is put under pressure, the content of the microcapsules is deposited on the rollers staining the back of the developing sheet at the time of following development. Furthermore, a thickened layer of capsule content laid upon the roller surface makes pressure distribution over the pair of pressure rollers less uniform, so that the developed image suffers uneven color quality.